The invention relates to an automatic, non-invasive blood pressure monitor and to a method for non-invasively measuring blood pressure with such a monitor.
Automatic electronic blood pressure monitors are known. These monitors determine the values of the systolic and the diastolic blood pressure e.g. on the basis of an oscillometric measurement. Other measurements are also known which may be based on electronic detection of Korotkoff sounds.
Automatic, electronic blood pressure measuring devices are usually applied on the upper arm of a patient, around the wrist or on a finger of the patient. While the measurement as such has proven to be sufficiently accurate with such devices, errors may occur due to the fact that a user is making movements during the measurement. Ideally, the blood pressure should be taken when the user is sitting down and has been at rest for some time.
It is a disadvantage of known blood pressure measuring devices, that wrong measurement values may be given if the device is not properly used, especially if the user did not rest sufficiently before the measurement. This is mainly the case with blood pressure monitors for the home use, such as oscillometric automatic blood pressure monitors.
It is an object of the present invention to overcome the drawbacks of the prior art, and in particular to provide an automatic, non-invasive blood pressure monitor suited for home use which allows reduction of measurement errors which are based on the fact that a user is moving during the measurement or does not rest sufficiently before the measurement. A further object of the invention is to provide a method for measuring the blood pressure which allows reduction of such errors.
Still a further object of the invention is to provide a non-invasive blood pressure monitor and a method for measuring the blood pressure which also allow fast determination of the blood pressure, if desired.
According to the present invention, these objects are solved with an automatic, non-invasive blood pressure monitor and with a method as described below.
The blood pressure monitor according to the present invention is operable in a first operating mode and in a second operating mode. In the first operating mode, blood pressure values are determined on the basis of one single measurement in a conventional manner.
In the second operating mode, the blood pressure values are calculated on the basis of a series of measurements. The inventive device can be used in the first operating mode for a quick and rough blood pressure measurement. The second operating mode allows a much more precise measurement. During a certain period of time, measurements are repeated and the value of the systolic and the diastolic blood pressure is determined as an average of several measurements. The second operating mode is especially advantageous because the measurement series lasts for a certain amount of time. While the first measurement may be still erroneous because of insufficient rest of the user, the following measurements will be more accurate because the user will normally sit or lie down during the measurements. The device therefore is suitable for home use.
In a preferred embodiment, the blood pressure monitor comprises means for switching between the first operating mode and the second operating mode. The user may at its discretion choose if a fast rough measurement or a slower and more accurate measurement shall be made.
The blood pressure monitor preferably comprises means for calculating or determining a statistical distribution of the measured values and means for forming an average of a number of measured blood pressure values.
The means for forming the average are preferably programmed in such a way that a weighted average may be calculated.
It must be noted that the first and the second operating mode are independent from each other. The blood pressure monitor could only be operated in the first operating mode or in the second operating mode if this should be desired by the user. xe2x80x9cFirstxe2x80x9d and xe2x80x9csecondxe2x80x9d does not relate to time sequences or a specific order or preference of the operating modes and it does not exclude other operating modes.
According to the method of the present invention, in the second operating mode an average value of the diastolic and the systolic blood pressure values is calculated and displayed.
In the second operating mode, a pause is preferably made between subsequent measurements. The pause can be about 60 seconds. This pause is advantageous in that it allows the measurement site (e.g. the upper arm or the wrist) to relax between measurements and in that it leads to an additional rest of the user.
In a further preferred embodiment, a statistical distribution of the blood pressure values is determined. Depending on the distribution, different calculation modes for calculating the average may be used. If one or more of the measured values substantially differs from the other measured values, a weighted average may be calculated. If all measured values are within a pre-determinable range, a normal, arithmetic average will be calculated.
In addition, if one or more of the measured values substantially differ from the others, an additional measurement may be made.
The method according to the present invention is also adapted to calculate the pulse rate with high accuracy. As the measurement lasts for quite a long time, a precise mean value of the pulse rate pressure may be calculated.